Pinworms

I really hope you're not eating right now, because pinworms may just be the grossest things kids can get. This description from KidsHealth describes it: "After getting in your mouth, the eggs pass through the digestive system. The eggs hatch in the small intestine, and the baby worms grow and move on to the large intestine. There, the pinworms grab onto the wall of the intestine. After a few weeks, the female pinworms move to the end of the large intestine, and they come out of the body at night to lay their eggs around the anus."